Question

compare the energy changes involved during a physical and a chemical change

Answer 1

In physical change the arrangement of molecules is altered leading to the state change of the matter. There is no change in molecular composition. The energy needed for a physical change is equal to the energy needed for reverse of the reaction. So there is no change in energy. Whereas in the case of chemical changes, there is energy change as the new bonds are formed and the old bonds are cleaved. Thus there is either release of energy (exothermic) or absorption of energy (endothermic)